There are size differences between species, but usually have to get much larger to split or to propagate (Oh, let's say about at least a quarter dollar size).
Harry,
Tell us what you've got - set up, water params, where you've placed it...ect.
Discosoma are easy to keep under moderate lighting and with good water quality. If you feed them small pieces of meaty foods, they'll "envelope" as they consume the food.